Traditional hard disc magnetic recording technology has long been believed to be subject to a physical capacity limit known as the super paramagnetic effect. The term refers to a point at which discrete magnetic areas on a disc surface becomes so tiny that their magnetic orientation was assumed to be unstable at room temperature, rendering the data storage unreliable.
Hard disc technology has also been limited by conventional magnetic head designs. A typical prior art Winchester magnetic storage system includes a magnetic head that has a slider element. A magnetic read/write element is coupled to a rotary actuator magnet and coil assembly by a suspension on the slider element. An actuator arm forming a part of the slider element and holding the coil assembly in suspension is positioned over a surface of a spinning magnetic disc. In operation, lift forces are generated by aerodynamic interactions between the magnetic head and the spinning magnetic disc, pulling the head away from the disc. The lift forces are opposed by equal and opposite spring forces applied by the suspension such that a predetermined flying height for the head is mainta over a full radial stroke of the rotary actuator assembly above the surface of the spinning magnetic disc.
Flying head designs have been proposed for use with magneto-optical storage technology, but have heretofore been difficult to realize in commerce. One factor that continues to limit MO disc drives is the physical size of the head necessary to hold the various components required for accessing magneto-optical information. Conventional magneto-optical heads, while providing access to magneto-optical discs with aerial densities on the order of 1 gigabit per square inch, have been based on relatively large optical assemblies, and the physical size and mass of the heads have made them rather bulky (on the order of 3-15 mm in a dimension). This is because the heads must carry both optics focusing the laser beam on a spot on the disc, and an electromagnetic coil surrounding the lens for establishing the applied magnetic field, which is also a part of the accessing process. A typical prior art head is shown in FIG. 1, which is an example of a present head design and a method for making it. In FIG. 1 the head was built up on a substrate 14 which is coated with a layer of alumina 15. In this example, two layers 10, 12 were deposited on the surface. These coils were energized to establish the magnetic field. A layer of permalloy 13 was plated over the top of the coils to assist in focussing the magnetic field generated by the coils on the media being accessed. The size and number of coils has been established in the technology and is not specifically discussed. At the edge of the head, bond pads 16 were provided to which wires were bonded to make attachments to the rest of the system. These wires were the leads for carrying signals away from the head. The coils 10, 12 surrounded an opening in the substrate 14 where a lens 18 was mounted which comprises the objective lens for focusing the laser output on the storage media to be accessed. A generally cylindrical graduated reflective index (GRIN) lens was adhesively attached to a vertical slot 17 in the slider and fixed in place there.
Among the difficulties posed by this design was that the heads are quite e fragile and thus difficult to process without substantial losses. Further, substantial heat was generated relative to the size of the head and it became difficult to successfully conduct the heat away from the head. Further, the device lacked dimensional stability, and had a tendency to curl.
Such systems had several limitations in addition to being subject to bending. The coils 10, 12 were relatively weak mechanically and difficult to align and attach to the slider body. In addition, the coils were thermally inefficient. The power dissipated in the coil during data writing operations caused the coil to heat and flex due to thermal expansion differences between the various layers.
A further difficulty with such designs was that the adhesive attachment of the cylindrical lens to a machine channel in the slider body. It did not allow accurate placement of the lens with respect to the other parts of the body, and did not allow the attachment of miniature, molded lenses for use in the head assembly. Further, the head being of extremely small dimension was extremely difficult to handle during mounting.